使用来自asp.net webservice的jquery解析简单的xml

I'm breaking my head over this for a while now and I have no clue what I do wrong. The scenario is as followed, I'm using swfupload to upload files with a progressbar via a webservice. the webservice needs to return the name of the generated thumbnail. This all goes well and though i prefer to get the returned data in json (might change it later in the swfupload js files) the default xml data is fine too.I'm breaking my head over this for a while now